The present invention relates to an optical switch for switching a combination of light paths between a plurality of optical fibers.
In common, an optical switch is provided for switching the light path between collimate lenses optically coupled to corresponding optical fibers by a prism advancing and retracting between two set of the lenses. Some of such conventional optical switches are disclosed having an electromagnetic driver equipped with an armature which is mechanically joined to the prism (U.S. Pat. No. 5,999,669 and JP Patent Laid-open Publication 4-145409).
The optical switch disclosed in U.S. Pat. No. 5,999,669 has a prism 31 arranged to move to and from between collimate lenses 35, which are optically coupled to corresponding optical fibers 4a to 4c and located at their position in a body 1, for switching the light path, as shown in FIG. 57. The prism 31 is mounted to one end of an arm 37 which is joined at the other end to and driven by a relay RY for rotation. As a result, the prism 31 is moved vertically of the sheet of paper to and from the light path. When the prism 31 is retracted from the light path, the two optical fibers 4a and 4c are coupled. When the prism 31 is set across the light path, the optical fiber 4a is coupled to the optical fiber 4b. 
The optical switch disclosed in JP Patent Laid-open Publication 4-145409 has a prism 31 arranged to move in and from between collimate lenses 35, which are optically coupled to corresponding optical fibers 4a, 4b, 4c, and 4d, through the window 38e provided in an iron core for switching the light path, as shown in FIG. 58. The prism 31 is actuated by a mechanism which has a leaf spring 38a joined at one end to a permanent magnet 38b and the prism 31 and at the other end to the iron core 38c. The iron core 38c has a coil 38d wound thereon. When the coil 38d is energized, a magnetic force is developed between the permanent magnet 38b and the iron core 38c thus to move the prism 31 to and from the light path vertically of the sheet of paper. When the prism 31 is retracted from the light path, the optical fibers 4a and 4b are coupled to the optical fibers 4c and 4d respectively. When the prism 31 is present across the light path, the optical fibers 4a and 4d are coupled to each other while the optical fibers 4b and 4c are coupled to each other.
In either the conventional optical switch, the prism 31 is mounted to the arm 37 or the leaf spring 38a which extends at a right angle to the moving direction of the prism 31. Also, as the arm 37 or the leaf spring 38a performs a pivotal movement about one pivot, its length has to be increased for extending the stroke of the movement of the prism 31.
As a result, the body 1 will be increased in the size along the lengthwise direction of the arm 37 or the leaf spring 38a. Also, the body 1 may have an unwanted dead space in the interior thereof. Since the prism 31 is pivotably moved about the pivot on the arm 37 or the leaf spring 38a, its pivotal movement permits the area of the prism 31 adjacent to the center thereof to be off the light path and causes the outermost of the prism 31 to travel a long distance. Accordingly, a more space will be needed for clearing the movement of the prism 31, hence increasing the overall size of the body 1.
It is hence an object of the present invention to provide an optical switch which is decreased in the overall size with any dead space minimized in its body.
In order to achieve the above-mentioned object, according to the present invention, an optical switch for switching the light path between collimate lenses optically coupled to the ends of corresponding optical fibers by the advancing and retracting movements of a prism, comprises: a body incorporating an optical switch housing; an electromagnetic driver having an armature arranged to hold the prism and a coil block for driving the movement of the armature by means of magnetic actions; and a leaf spring resilient in the moving direction of the armature consisting mainly of at least two parallelly extending spring strips, each of the spring strips is fixedly mounted at one end to the body and at the other end to the armature thus to spatially hold the armature and the prism for linear movement. The electromagnetic driver and the prism are disposed next to each other along the moving direction of the armature, and the armature and the prism can linearly be moved at a right angle to the light path between the lenses when the optical switch is in action.
As one feature of the present invention, the electromagnetic driver allows the armature and thus the prism to move linearly. Also, the electromagnetic driver is located next to the prism along the moving direction of the armature. Accordingly, the size for advancing and retracting the prism is determined simply by the area of the prism projected on a place orthogonal to the moving direction of the armature. As a result, the mechanism for switching the light path can be minimized in the dimensions. Also, as the movement of the prism is linear, unlike the conventional pivotal movement about a pivot point on a member to which the prism is mounted, any dead apace for clearing the movement of the prism will be eliminated. Consequently, the body can be decreased in the overall size.
In the optical switch of the present invention, the coil block in the electromagnetic driver comprises an iron core having two magnetic polar portions provided at both ends thereof, a coil for exciting the iron core, and a permanent magnet for magnetizing the armature, the armature comprises a first contact portion located opposite to one side of one of the two magnetic polar portions which faces one direction of the movement of the armature and a second contact portion located opposite to one side of the other magnetic polar portion which faces the other direction of the movement of the armature, and each of the spring strips is joined to an intermediate region between the two contact portions of the armature. As the electromagnetic driver is of a polar type, it can generate a large driving force from a relatively small level of current thus contributing to the energy saving.
In the optical switch of the present invention, the electromagnetic driver performs a bistable action for holding the armature by the magnetic force of the permanent magnet at each of the two positions, where the first contact portion of the armature comes into direct contact with the corresponding polar portion of the iron core and where the second contact portion of the armature comes into direct contact with the other polar portion of the iron core. As the electromagnetic driver performs the bistable action, its coil has to be energized only when the switching of the light path is required hence minimizing the consumption of power.
In the optical switch of the present invention, the electromagnetic driver performs a monostable action for holding the armature by the magnetic force of the permanent magnet constantly at one of the two positions, where the first contact portion of the armature comes into direct contact with the corresponding polar portion of the iron core or where the second contact portion of the armature comes into direct contact with the other polar portion of the iron core. As the electromagnetic driver performs the monostable action, its coil needs not to be energized while normally connected one of the light path is selected hence minimizing the consumption of power.
In the optical switch of the present invention, the number of the spring strips is four, and the armature is arranged between two pairs of the spring strips, each pair extending in one direction from each joint with the armature to one of the magnetic polar portion. As the armature is supported at both ends along the direction across the two polar portions of the iron core, its movement can substantially be inhibited along a direction which extends at a right angle to the moving direction of the armature and to the direction aligned across the two polar portions. More specifically, when the armature remains at its contact portion in direct contact with the corresponding polar portion of the iron core, its movement are inhibited along the direction at a right angle to the moving direction of the armature and to the direction aligned across the two polar portions hence inhibiting the prism from being dislocated by any external impact. As a result, the possibility of changing the light path or the intensity of light along the light path due to the action of any external stress can successfully be eliminated. As the number of the spring segments is four, those effects can be more emphasized than with two spring segments.
In the optical switch of the present invention, the leaf spring has a joint strip thereof arranged extending in the moving direction of the armature and joined to the armature along the movement in an overlap relationship while the spring strips are arranged integrally with the ends of the joint strip in the moving direction of the armature. Accordingly, the spring segments can be prevented from deflecting during their assembling with the armature. This allows the spring strips to be mounted to the armature with no deflection. Also, as the joint strip of the leaf spring is oriented along the moving direction of the armature, its assembling action can be carried out with ease at the widely open side of the armature.
The optical switch of the present invention allows the prism to be joined to the armature with the use of no particular components and can thus be decreased in the number of components, the overall dimensions, and the production cost. Also, the positional precision of the prism can be ensured by controlling the size of the armature. As a result, the positioning of the prism can be stabilized and improved.
The optical switch of the present invention has the prism holder platform joined integral with the armature while not interrupting the action of the leaf spring.
The optical switch of the present invention has the branches and frame of the leaf spring provided to surround the prism holder platform thus increasing the resistance against any unwanted impact of force along the direction orthogonal to the moving direction of the armature and the lengthwise direction of the spring.
The optical switch of the present invention allows the positional relationship between the armature and the prism to be finely controlled thus minimizing a declination in the intensity of light along the light path between the two sets of the collimate lenses.
The optical switch of the present invention allows the positioning of the components of the electromagnetic driver and the prism in relation to the body to be determined with reference to the iron core, thus minimizing discrepancies between different sample lots.
The optical switch of the present invention has the side wall and the bottom wall of the lens holder platform to be formed integral with each other to develop an L shape in the cross section, hence increasing the physical strength of the lens holder platform even with its side wall and bottom wall arranged thinned. When its strength is desired of a level equal to that of any conventional switch, the lens holder platform can be decreased in the overall size. When its size is desired of a level equal to that of any convention switch, the lens holder platform can spare a more room for the movement of the prism which is thus implemented with much ease.
The optical switch of the present invention has the iron core defining the movement of the armature and the lens holder platform determining the position of the lenses to be joined to each other, thus controlling at high precision the positional relationship between the lenses and the prism. Also, the optical axes of the lenses can accurately be aligned with the prism.